B cells are lymphoid stem cells from the bone marrow that migrate to and become mature antigen-specific cells in the spleen and lymph nodes. Many immature B cells are found in the spleen which, because of the large amount of blood passing through it, provides many chances for the B cells to become exposed to new antigens. This promotes differentiation of the B cells into functional cells. Mature B cells are capable of being stimulated by specific antigens which enter into the body. After B cells come in contact with antigens, they change into plasma cells and produce antibodies which destroy the invading antigens. This antigen-antibody reaction is known as the specific immune response.
Hybridoma cell lines are created by fusing B cells with NSO murine myeloma cells. These myeloma cells are from tumors which originate in the bone marrow. When B cells and NSO myeloma cells are fused, hybridomas are produced, which hybridomas secrete monoclonal antibodies.
Monoclonal antibodies are exceptionally pure and antigen-specific antibodies. Monoclonal antibodies are used to identify antigens on viruses and bacteria, and are also used in tissue and blood typing. Further, monoclonal antibodies can be used to identify hormones, to diagnose infectious diseases and to identify tumor antigens.
When certain populations of B cells are used to produce monoclonal antibodies, low affinity antibodies, which do not bind effectively with antigens, are produced. Further, some B cells undergo apoptotic cell death, especially B cells making antibodies to self-antigens, and do not result in the production of viable hybridomas. Therefore, a need exists to develop hybridomas which are more resistant to death, which hybridomas secrete monoclonal antibodies which are high affinity, and therefore bind effectively to antigens.
Further, when B cells proliferate in lymphoid organs, somatic mutations of immunoglobulin genes occurs, which leads to the generation of clonally related B cells which have diversified antigen receptors. Within this population of B cells, antigen selection results in affinity maturation. As pathogenic autoantibodies are encoded by somatically mutated immunoglobulin genes, autoantigenic specificity may be acquired by the process of somatic hypermutation. These autoreactive cells represent the pathogenic B cells of autoimmune disease.
Autoimmune diseases are diseases which are produced when the body's normal tolerance of its own antigenic markers on cells disappears. Autoantibodies are produced by B cells, and these autoantibodies attack normal cells whose surface contains a "self" antigen or autoantigen. This results in the destruction of tissue. Therefore, a need exists to develop monoclonal antibodies which are specific for, bind to and thereby inactivate cells which produce autoantibodies.
It is therefore an object of this invention to provide a cell line which has a high fusion frequency when used to produce monoclonal antibody-secreting hybridomas.
It is a further object of this invention to provide monoclonal antibody-secreting hybridomas which have increased resistance to death.
It is another object of this invention to provide a method of producing monoclonal antibody-secreting hybridomas which have increased resistance to death.
It is a still further object of this invention to provide hybridomas which secrete monoclonal antibodies which have increased affinity for foreign antigens.
It is a yet another object of this invention to provide monoclonal antibodies which have increased affinity for autoantibody-producing cells.